Oil and gas wells are often stimulated by fracturing or other treatments to enhance production. Wellbores, particularly long horizontal wellbores, are typically stimulated at a plurality of zones or stages. A completion string is fit with a plurality of completion valves spaced therealong. Some multi-zone fracturing shifting tools are used to open or close completion valves. This tool contains a set of shifting dogs that are held or biased outwardly by springs. The shifting dogs are profiled on a downhole face so as to pass down through the sleeve, repeatedly being ramped radially inwardly by the profile to pass narrow bore portions. When pulled back up through the sleeve, an uphole profile of the dogs will latch into a sleeve shifting profile, and pulling the dogs further up shifts the sleeve open.
As shown in FIGS. 1A and 1B, a prior art flow-shifting tool is configured to actuate the dogs D hydraulically by pumping fluid through the tool. The dogs are spring-biased to extend radially outwardly but are temporarily held radially inwardly by a retainer sleeve S so they cannot latch into any shifting profiles until fluid is pumped through the tool, shifting the sleeve and disengaging the dogs to enable extension thereof.
Currently, there are a number of different ways to complete a system in this manner. One way, as developed by the Applicant, is to run the flow-shifting tool of FIGS. 1A and 1B coupled to a J-slot resealable packer tool. Once the shifting tool has been used to open the completion valve the J-slot is shifted and the packer is set below the valve, isolating the open valve from any previously opened valves therebelow. After the treatment is completed, the J-slot is shifted, the packer is disengaged, and the flow-shifting tool is moved up to open the next valve.
As shown in FIG. 2, another way is to run two opposing shifting tools at the same time to provide two opposing shifting profiles SP1, SP2 in the frac valve sleeve. One shifting tool, having uphole catches, is used to open the valve to expose frac ports FP by pulling up. The frac is placed, and then the other opposing shifting tool, having downhole catches, is used to re-close that valve. With the open and close capability, valves are opened, fractured, and then closed as the tool moves up the well. Once all valves have been fractured, they are all re-opened to produce the well.
FIGS. 3 and 4 show a mechanical resealable packer commonly used in the frac tools, which is also called a J-slot packer. The packer has a packer element PE, a setting cone SC, casing slips CS, and drag blocks DB, all supported on a mandrel M. The packer element PE is set and reset by varying the position of a pin P riding in a revolving J-slot profile J that is machined into the mandrel. As the tool is cycled up and down in the well bore, the pin in the profile moves the tool from a “run-in-hole” position (i.e. with the packer element retracted) to a “pull-out-of-hole” position (i.e. with the packer element retracted), then to a “set” position (i.e. with the packer element set or expanded), and then back to a “pull-out-of-hole” position. The pin is in the “run-in-hole” (RIH) slot of the J-slot profile when the tool is in the run-in-hole position; the pin is in the “pull-out-of-hole” (POOH) slot of the J-slot profile when the tool is in the pull-out-of-hole position; and the pin is in the “set” (SET) slot of the J-slot profile when the tool is in the set position.
As shown in FIG. 4, the J-slot pattern for cycling the tool between the run-in-hole, pull-out-of-hole, and set positions spans the entire circumference of the mandrel so as to repeat about the circumference of the mandrel. The J-slot mechanism can be cycled to place the tool in a desired position. For example, occasionally sand can get in the J-slot and temporarily limit the pin's movement, or while running in hole the pin can skip over a slot, thereby placing the tool in a different position than intended. The tool can be placed in the desired position again by cycling through the slots in the J-slot profile.
Applicant contemplated mechanically activating a shifting tool in a similar manner. In addition to engaging casing slips to set the packer in the casing, a J-slot mechanism can also be used to expand and retract shifting dogs for shifting open a frac valve sleeve. The challenge in doing so is that the tool string would then have two separate J-slots working opposite and independently from one another. The two J-slots have to function such that when the packer J-slot is in the “set” position, the next pull up on the shifting J-slot would have to be in the shifting tool's “set” position (i.e. with the shifting dogs in an expanded position) to open the sleeve. However, if one of the two J-slots ends up jamming or skipping into the different position unintentionally, as described above, the two independent J-slots are then thrown out of sync and will not operate as expected. Depending on how the double J-slot tool is configured, both the packer and the dogs could be set and the tool could potentially be stuck in the well, thereby preventing the tool from moving up or down because the tool keeps “setting” in either direction.